Elephant Polo
We don't want to take credit for others inventions we are purely the masters at this sport.
Some more
Economics
Golf (and don't start with yer Chinese/Dutch mince ;bat;)
Logarithms
US Navy (okay maybe not too much credit there)
And one for Kev: Microwave Ovens
FFS Tank had to go and change half my post but great post, in keeping with our overall excellence